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They also picked up three of the six seats they need to win the Senate, but needed a virtual sweep of other too-close-to call races to grab control of the upper chamber, as they strive to handcuff Bush in his last two years in office.

 Democrats ousted incumbents in Connecticut, Indiana, Kentucky, New Hampshire, North Carolina, Ohio, Pennsylvania and Rhode Island, according to early television network projections.

 In what was shaping up as a banner night for the Democratic party, Keith Ellison from Minnesota became the first Muslim elected to Congress, and Hillary Clinton as expected crushed her Republican rival to claim a second term in the Senate.

 Democrat Senate campaign manager Chuck Schumer kept expectations in check, however, as his party targeted control of the 435-seat House of Representatives and 100-member Senate.

 "We're not breaking out the champagne bottles yet. It's going to be a long night. But so far, so good," Schumer told supporters at party headquarters here.

 Democrats in midwestern Indiana led the charge, ousting Republicans in three seats. A Republican incumbent was also toppled in Kentucky.

 House Republicans also fell in New Hampshire, North Carolina and Ohio and senior House member Curt Weldon and another Republican also tumbled in Pennsylvania, leaving Democrats needing another five scalps to take control of the lower chamber.

 Democrats also picked up three of the six seats they needed in the Senate, with Democrat Bob Casey projected to beat conservative Republican Senator Rick Santorum in Pennsylvania.

 As expected, outgoing Ohio House member Sherrod Brown ousted Republican Senator Mike DeWine, according to network calls, in a state badly hit by economic problems and the deaths of reserve soldiers in Iraq.

 And maverick Republican Senator Lincoln Chafee of Rhode Island also lost, despite parting with Bush on several key foreign policy questions, networks projected.

 US media also said Democrats would retain contested New Jersey and Maryland seats.

 But the opposition party would still need a stunning sweep of three of the four remaining key Senate races in Virginia, Montana, Tennessee and Missouri which were too close to call.

 Americans were also electing state governors on Tuesday and Democrats picked up five governorships according to television projections.

 As millions of people went to the polls, problems with electronic voting machines were reported across the country, forcing authorities in some states to extend voting hours. Both sides hurled accusations of voter fraud.

 Early exit poll data by the ABC television network showed that six in 10 voters disapproved of the way Bush was doing his job. Six in 10 voters also disapproved of the Iraq war.

 CBS exit polls found 57 per cent of voters disapproved of the war in Iraq, which has claimed the lives of more than 2,800 soldiers.

 CNN exit surveys found 41 per cent of voters found corruption was an extremely important issue in their choice, possibly a bad sign for Republicans who suffered a string of financial and moral scandals after years in power.

 Some 40 per cent of those asked in the CNN poll said terrorism was an important factor and 36 per cent said Iraq was.

 Democratic National Committee chairman Howard Dean said on CNN that a large turnout could benefit his party.

 "Seeing all those people come out to vote is a really good thing for the country and makes us optimistic. Because we know people want change and it looks like they're acting on it tonight."

 But control of the upper chamber will depend on whether Democrats can win toss-up Senate races in Virginia, Tennessee, Missouri and Montana.

 Bush sweated it out in the White House, set to watch results that could help set his legacy in stone, with Karl Rove, his right-hand man since his earliest days in Texas politics.

 "The president is in a good mood," said spokesman Tony Snow, after the president flew to Washington after voting in his adopted hometown of Crawford, Texas.

 A judge ordered 55 polling stations in Lebanon County, Pennsylvania, to remain open for an extra hour following a programming error in voting machines.

 Voting machines also broke down and there was voter confusion in towns in Ohio, Florida, and Colorado.

 FBI agents in Virginia investigated claims of voter intimidation lodged by Democrats.

 Democrats used the election as a referendum on Bush, and Iraq.

 Bush accused his rivals of having no plan to win the war, and said only the Republicans could give full protection against terrorists.

 "Harsh criticism is not a plan for victory. Second-guessing is not a strategy," Bush told supporters in Texas Monday.

 As well as Iraq, the election will also hinge on how much issues like skyrocketing health-care costs; "values" issues like stem-cell research, gay marriage and abortion; the economy and illegal immigration.

 Turnout has averaged about 40 per cent for midterm elections over the past three decades, but many experts have said it could be substantially higher this time.

Agence France Presse